import argparse
import datetime
import numpy as np
import time
import torch
import torch.backends.cudnn as cudnn
import json
import os
from functools import partial
from pathlib import Path
from collections import OrderedDict

from timm.models import create_model
from timm.utils import ModelEma
from optim_factory import create_optimizer, get_parameter_groups, LayerDecayValueAssigner

from datasets import build_dataset
from engines.engine_for_finetuning_regression import train_one_epoch, validation_one_epoch, final_test, merge
from utils import NativeScalerWithGradNormCount as NativeScaler
from utils import multiple_samples_collate
import utils
import contextlib
from models import *


def get_args():
    parser = argparse.ArgumentParser('VideoMAE fine-tuning and evaluation script for video classification', add_help=False)
    parser.add_argument('--batch_size', default=64, type=int)
    parser.add_argument('--epochs', default=30, type=int)
    parser.add_argument('--update_freq', default=1, type=int)
    parser.add_argument('--save_ckpt_freq', default=100, type=int)

    # Model parameters
    parser.add_argument('--model', default='vit_base_patch16_224', type=str, metavar='MODEL',
                        help='Name of model to train')
    parser.add_argument('--tubelet_size', type=int, default=2)
    parser.add_argument('--orig_t_size', type=int, default=8)
    parser.add_argument('--input_size', default=224, type=int,
                        help='videos input size')
    parser.add_argument('--use_learnable_pos_emb', action='store_true')
    parser.set_defaults(use_learnable_pos_emb=False)

    parser.add_argument('--fc_drop_rate', type=float, default=0.0, metavar='PCT',
                        help='Dropout rate (default: 0.)')
    parser.add_argument('--drop', type=float, default=0.0, metavar='PCT',
                        help='Dropout rate (default: 0.)')
    parser.add_argument('--attn_drop_rate', type=float, default=0.0, metavar='PCT',
                        help='Attention dropout rate (default: 0.)')
    parser.add_argument('--drop_path', type=float, default=0.1, metavar='PCT',
                        help='Drop path rate (default: 0.1)')

    parser.add_argument('--disable_eval_during_finetuning', action='store_true', default=False)
    parser.add_argument('--model_ema', action='store_true', default=False)
    parser.add_argument('--model_ema_decay', type=float, default=0.9999, help='')
    parser.add_argument('--model_ema_force_cpu', action='store_true', default=False, help='')

    # Optimizer parameters
    parser.add_argument('--opt', default='adamw', type=str, metavar='OPTIMIZER',
                        help='Optimizer (default: "adamw"')
    parser.add_argument('--opt_eps', default=1e-8, type=float, metavar='EPSILON',
                        help='Optimizer Epsilon (default: 1e-8)')
    parser.add_argument('--opt_betas', default=None, type=float, nargs='+', metavar='BETA',
                        help='Optimizer Betas (default: None, use opt default)')
    parser.add_argument('--clip_grad', type=float, default=None, metavar='NORM',
                        help='Clip gradient norm (default: None, no clipping)')
    parser.add_argument('--momentum', type=float, default=0.9, metavar='M',
                        help='SGD momentum (default: 0.9)')
    parser.add_argument('--weight_decay', type=float, default=0.05,
                        help='weight decay (default: 0.05)')
    parser.add_argument('--weight_decay_end', type=float, default=None, help="""Final value of the
        weight decay. We use a cosine schedule for WD and using a larger decay by
        the end of training improves performance for ViTs.""")

    parser.add_argument('--lr', type=float, default=1e-3, metavar='LR',
                        help='learning rate (default: 1e-3)')
    parser.add_argument('--layer_decay', type=float, default=0.75)

    parser.add_argument('--warmup_lr', type=float, default=1e-6, metavar='LR',
                        help='warmup learning rate (default: 1e-6)')
    parser.add_argument('--min_lr', type=float, default=1e-6, metavar='LR',
                        help='lower lr bound for cyclic schedulers that hit 0 (1e-6)')

    parser.add_argument('--warmup_epochs', type=int, default=5, metavar='N',
                        help='epochs to warmup LR, if scheduler supports')
    parser.add_argument('--warmup_steps', type=int, default=-1, metavar='N',
                        help='num of steps to warmup LR, will overload warmup_epochs if set > 0')

    # Augmentation parameters
    parser.add_argument('--color_jitter', type=float, default=0.4, metavar='PCT',
                        help='Color jitter factor (default: 0.4)')
    parser.add_argument('--num_sample', type=int, default=2,
                        help='Repeated_aug (default: 2)')
    parser.add_argument('--aa', type=str, default='rand-m7-n4-mstd0.5-inc1', metavar='NAME',
                        help='Use AutoAugment policy. "v0" or "original". " + "(default: rand-m7-n4-mstd0.5-inc1)'),
    parser.add_argument('--smoothing', type=float, default=0.,
                        help='Label smoothing (default: 0.)')
    parser.add_argument('--train_interpolation', type=str, default='bicubic',
                        help='Training interpolation (random, bilinear, bicubic default: "bicubic")')

    # Evaluation parameters
    parser.add_argument('--crop_pct', type=float, default=None)
    parser.add_argument('--short_side_size', type=int, default=224)
    parser.add_argument('--test_num_segment', type=int, default=5)
    parser.add_argument('--test_num_crop', type=int, default=3)
    
    # Random Erase params
    parser.add_argument('--reprob', type=float, default=0.25, metavar='PCT',
                        help='Random erase prob (default: 0.25)')
    parser.add_argument('--remode', type=str, default='pixel',
                        help='Random erase mode (default: "pixel")')
    parser.add_argument('--recount', type=int, default=1,
                        help='Random erase count (default: 1)')
    parser.add_argument('--resplit', action='store_true', default=False,
                        help='Do not random erase first (clean) augmentation split')

    # Mixup params
    parser.add_argument('--mixup', type=float, default=0.,
                        help='mixup alpha, mixup enabled if > 0.')
    parser.add_argument('--cutmix', type=float, default=0.,
                        help='cutmix alpha, cutmix enabled if > 0.')
    parser.add_argument('--cutmix_minmax', type=float, nargs='+', default=None,
                        help='cutmix min/max ratio, overrides alpha and enables cutmix if set (default: None)')
    parser.add_argument('--mixup_prob', type=float, default=1.0,
                        help='Probability of performing mixup or cutmix when either/both is enabled')
    parser.add_argument('--mixup_switch_prob', type=float, default=0.5,
                        help='Probability of switching to cutmix when both mixup and cutmix enabled')
    parser.add_argument('--mixup_mode', type=str, default='batch',
                        help='How to apply mixup/cutmix params. Per "batch", "pair", or "elem"')

    # Finetuning params
    parser.add_argument('--finetune', default='', help='finetune from checkpoint')
    parser.add_argument('--delete_head', action='store_true', help='whether delete head')
    parser.add_argument('--model_key', default='model|module', type=str)
    parser.add_argument('--model_prefix', default='', type=str)
    parser.add_argument('--init_scale', default=0.001, type=float)
    parser.add_argument('--use_checkpoint', action='store_true')
    parser.set_defaults(use_checkpoint=False)
    parser.add_argument('--checkpoint_num', default=0, type=int,
                        help='number of layers for using checkpoint')
    parser.add_argument('--use_mean_pooling', action='store_true')
    parser.set_defaults(use_mean_pooling=True)
    parser.add_argument('--use_cls', action='store_false', dest='use_mean_pooling')

    # Dataset parameters
    parser.add_argument('--prefix', default='', type=str, help='prefix for data')
    parser.add_argument('--split', default=' ', type=str, help='split for metadata')
    parser.add_argument('--filename_tmpl', default='img_{:05}.jpg', type=str, help='file template')
    parser.add_argument('--data_path', default='you_data_path', type=str,
                        help='dataset path')
    parser.add_argument('--eval_data_path', default=None, type=str,
                        help='dataset path for evaluation')
    parser.add_argument('--nb_classes', default=400, type=int,
                        help='number of the classification types')
    parser.add_argument('--imagenet_default_mean_and_std', default=True, action='store_true')
    parser.add_argument('--use_decord', action='store_true',
                        help='whether use decord to load video, otherwise load image')
    parser.add_argument('--no_use_decord', action='store_false', dest='use_decord')
    parser.set_defaults(use_decord=True)
    parser.add_argument('--num_segments', type=int, default=1)
    parser.add_argument('--num_frames', type=int, default=16)
    parser.add_argument('--sampling_rate', type=int, default=4)
    parser.add_argument('--trimmed', type=int, default=60)
    parser.add_argument('--time_stride', type=int, default=16)
    parser.add_argument('--data_set', default='Kinetics', choices=[
        'Kinetics', 'Kinetics_sparse', 
        'SSV2', 'UCF101', 'HMDB51', 'image_folder',
        'mitv1_sparse', 'LVU', 'COIN', 'Breakfast'
        ], type=str, help='dataset')
    parser.add_argument('--output_dir', default='',
                        help='path where to save, empty for no saving')
    parser.add_argument('--log_dir', default=None,
                        help='path where to tensorboard log')
    parser.add_argument('--device', default='cuda',
                        help='device to use for training / testing')
    parser.add_argument('--seed', default=0, type=int)
    parser.add_argument('--resume', default='',
                        help='resume from checkpoint')
    parser.add_argument('--auto_resume', action='store_true')
    parser.add_argument('--no_auto_resume', action='store_false', dest='auto_resume')
    parser.set_defaults(auto_resume=True)

    parser.add_argument('--save_ckpt', action='store_true')
    parser.add_argument('--no_save_ckpt', action='store_false', dest='save_ckpt')
    parser.set_defaults(save_ckpt=True)

    parser.add_argument('--start_epoch', default=0, type=int, metavar='N',
                        help='start epoch')
    parser.add_argument('--test_best', action='store_true',
                        help='Whether test the best model')
    parser.add_argument('--eval', action='store_true',
                        help='Perform evaluation only')
    parser.add_argument('--dist_eval', action='store_true', default=False,
                        help='Enabling distributed evaluation')
    parser.add_argument('--num_workers', default=10, type=int)
    parser.add_argument('--pin_mem', action='store_true',
                        help='Pin CPU memory in DataLoader for more efficient (sometimes) transfer to GPU.')
    parser.add_argument('--no_pin_mem', action='store_false', dest='pin_mem')
    parser.set_defaults(pin_mem=True)
    parser.add_argument('--no_amp', action='store_true')
    parser.set_defaults(no_amp=False)

    # distributed training parameters
    parser.add_argument('--world_size', default=1, type=int,
                        help='number of distributed processes')
    parser.add_argument('--local_rank', default=-1, type=int)
    parser.add_argument('--dist_on_itp', action='store_true')
    parser.add_argument('--dist_url', default='env://',
                        help='url used to set up distributed training')

    parser.add_argument('--enable_deepspeed', action='store_true', default=False)
    parser.add_argument('--bf16', default=False, action='store_true')

    known_args, _ = parser.parse_known_args()

    if known_args.enable_deepspeed:
        try:
            import deepspeed
            from deepspeed import DeepSpeedConfig
            parser = deepspeed.add_config_arguments(parser)
            ds_init = deepspeed.initialize
        except:
            print("Please 'pip install deepspeed'")
            exit(0)
    else:
        ds_init = None

    return parser.parse_args(), ds_init


def main(args, ds_init):
    utils.init_distributed_mode(args)

    if ds_init is not None:
        utils.create_ds_config(args)

    print(args)

    device = torch.device(args.device)

    # fix the seed for reproducibility
    seed = args.seed + utils.get_rank()
    torch.manual_seed(seed)
    np.random.seed(seed)
    # random.seed(seed)

    cudnn.benchmark = True

    dataset_train, args.nb_classes = build_dataset(is_train=True, test_mode=False, args=args)
    assert args.nb_classes == 1, "nb_classes should be 1 for regression"
    if args.disable_eval_during_finetuning:
        dataset_val = None
    else:
        dataset_val, _ = build_dataset(is_train=False, test_mode=False, args=args)
    dataset_test, _ = build_dataset(is_train=False, test_mode=True, args=args)
    

    num_tasks = utils.get_world_size()
    global_rank = utils.get_rank()
    sampler_train = torch.utils.data.DistributedSampler(
        dataset_train, num_replicas=num_tasks, rank=global_rank, shuffle=True
    )
    print("Sampler_train = %s" % str(sampler_train))
    if args.dist_eval:
        if len(dataset_val) % num_tasks != 0:
            print('Warning: Enabling distributed evaluation with an eval dataset not divisible by process number. '
                    'This will slightly alter validation results as extra duplicate entries are added to achieve '
                    'equal num of samples per-process.')
        sampler_val = torch.utils.data.DistributedSampler(
            dataset_val, num_replicas=num_tasks, rank=global_rank, shuffle=False)
        sampler_test = torch.utils.data.DistributedSampler(
            dataset_test, num_replicas=num_tasks, rank=global_rank, shuffle=False)
    else:
        sampler_val = torch.utils.data.SequentialSampler(dataset_val)

    if global_rank == 0 and args.log_dir is not None:
        os.makedirs(args.log_dir, exist_ok=True)
        log_writer = utils.TensorboardLogger(log_dir=args.log_dir)
    else:
        log_writer = None

    if args.num_sample > 1:
        collate_func = partial(multiple_samples_collate, fold=False)
    else:
        collate_func = None

    data_loader_train = torch.utils.data.DataLoader(
        dataset_train, sampler=sampler_train,
        batch_size=args.batch_size,
        num_workers=args.num_workers,
        pin_memory=args.pin_mem,
        drop_last=True,
        collate_fn=collate_func,
        persistent_workers=True
    )

    if dataset_val is not None:
        data_loader_val = torch.utils.data.DataLoader(
            dataset_val, sampler=sampler_val,
            batch_size=int(1.5 * args.batch_size),
            num_workers=args.num_workers,
            pin_memory=args.pin_mem,
            drop_last=False,
            persistent_workers=True
        )
    else:
        data_loader_val = None

    if dataset_test is not None:
        data_loader_test = torch.utils.data.DataLoader(
            dataset_test, sampler=sampler_test,
            batch_size=args.batch_size,
            num_workers=args.num_workers,
            pin_memory=args.pin_mem,
            drop_last=False,
            persistent_workers=True
        )
    else:
        data_loader_test = None

    if 'deit' in args.model:
        model = create_model(
            args.model,
            pretrained=True,
            num_classes=args.nb_classes,
            fc_drop_rate=args.fc_drop_rate,
            drop_path_rate=args.drop_path,
            kernel_size=args.tubelet_size,
            num_frames=args.num_frames,
        )
    elif 'videomamba' in args.model:
        model = create_model(
            args.model,
            img_size=args.input_size,
            pretrained=False if args.finetune else True,
            num_classes=args.nb_classes,
            fc_drop_rate=args.fc_drop_rate,
            drop_path_rate=args.drop_path,
            kernel_size=args.tubelet_size,
            num_frames=args.num_frames,
            use_checkpoint=args.use_checkpoint,
            checkpoint_num=args.checkpoint_num,
        )
    else:
        model = create_model(
            args.model,
            pretrained=False,
            num_classes=args.nb_classes,
            all_frames=args.num_frames * args.num_segments,
            tubelet_size=args.tubelet_size,
            use_learnable_pos_emb=args.use_learnable_pos_emb,
            fc_drop_rate=args.fc_drop_rate,
            drop_rate=args.drop,
            drop_path_rate=args.drop_path,
            attn_drop_rate=args.attn_drop_rate,
            drop_block_rate=None,
            use_checkpoint=args.use_checkpoint,
            checkpoint_num=args.checkpoint_num,
            use_mean_pooling=args.use_mean_pooling,
            init_scale=args.init_scale,
        )

    patch_size = model.patch_embed.patch_size
    print("Patch size = %s" % str(patch_size))
    args.window_size = (args.num_frames // args.tubelet_size, args.input_size // patch_size[0], args.input_size // patch_size[1])
    args.patch_size = patch_size

    if args.finetune:
        if args.finetune.startswith('https'):
            checkpoint = torch.hub.load_state_dict_from_url(
                args.finetune, map_location='cpu', check_hash=True)
        else:
            checkpoint = torch.load(args.finetune, map_location='cpu')

        print("Load ckpt from %s" % args.finetune)
        checkpoint_model = None
        for model_key in args.model_key.split('|'):
            if model_key in checkpoint:
                checkpoint_model = checkpoint[model_key]
                print("Load state_dict by model_key = %s" % model_key)
                break
        if checkpoint_model is None:
            checkpoint_model = checkpoint

        if 'head.weight' in checkpoint_model.keys():
            if args.delete_head:
                print("Removing head from pretrained checkpoint")
                del checkpoint_model['head.weight']
                del checkpoint_model['head.bias']
            elif checkpoint_model['head.weight'].shape[0] == 710:
                if args.nb_classes == 400:
                    checkpoint_model['head.weight'] = checkpoint_model['head.weight'][:args.nb_classes]
                    checkpoint_model['head.bias'] = checkpoint_model['head.bias'][:args.nb_classes]
                elif args.nb_classes in [600, 700]:
                    # download from https://drive.google.com/drive/folders/17cJd2qopv-pEG8NSghPFjZo1UUZ6NLVm
                    map_path = f'k710/label_mixto{args.nb_classes}.json'
                    print(f'Load label map from {map_path}')
                    with open(map_path) as f:
                        label_map = json.load(f)
                    checkpoint_model['head.weight'] = checkpoint_model['head.weight'][label_map]
                    checkpoint_model['head.bias'] = checkpoint_model['head.bias'][label_map]
                    
        all_keys = list(checkpoint_model.keys())
        new_dict = OrderedDict()
        for key in all_keys:
            if key.startswith('backbone.'):
                new_dict[key[9:]] = checkpoint_model[key]
            elif key.startswith('encoder.'):
                new_dict[key[8:]] = checkpoint_model[key]
            else:
                new_dict[key] = checkpoint_model[key]
        checkpoint_model = new_dict

        # interpolate position embedding
        if 'deit' in args.model or 'videomamba' in args.model:
            pos_embed_checkpoint = checkpoint_model['pos_embed']
            embedding_size = pos_embed_checkpoint.shape[-1] # channel dim
            num_patches = model.patch_embed.num_patches # 
            num_extra_tokens = model.pos_embed.shape[-2] - num_patches # 0/1
            orig_size = int((pos_embed_checkpoint.shape[-2] - num_extra_tokens) ** 0.5)
            # height (== width) for the new position embedding
            new_size = int(num_patches ** 0.5)

            if orig_size != new_size:
                print("Position interpolate from %dx%d to %dx%d" % (orig_size, orig_size, new_size, new_size))
                extra_tokens = pos_embed_checkpoint[:, :num_extra_tokens]
                # only the position tokens are interpolated
                pos_tokens = pos_embed_checkpoint[:, num_extra_tokens:]
                # B, L, C -> B, H, W, C -> B, C, H, W
                pos_tokens = pos_tokens.reshape(-1, orig_size, orig_size, embedding_size).permute(0, 3, 1, 2)
                pos_tokens = torch.nn.functional.interpolate(
                    pos_tokens, size=(new_size, new_size), mode='bicubic', align_corners=False)
                # B, C, H, W -> B, H, W, C ->  B, H, W, C
                pos_tokens = pos_tokens.permute(0, 2, 3, 1).reshape(-1, new_size, new_size, embedding_size) 
                pos_tokens = pos_tokens.flatten(1, 2) # B, L, C
                new_pos_embed = torch.cat((extra_tokens, pos_tokens), dim=1)
                checkpoint_model['pos_embed'] = new_pos_embed
            
            # we use 8 frames for pretraining
            temporal_pos_embed = checkpoint_model['temporal_pos_embedding']
            orig_t_size = args.orig_t_size // model.patch_embed.tubelet_size
            new_t_size = args.num_frames // model.patch_embed.tubelet_size
            # height (== width) for the checkpoint position embedding
            if orig_t_size != new_t_size:
                print(f"Temporal interpolate from {orig_t_size} to {new_t_size}")
                temporal_pos_embed = temporal_pos_embed.permute(0, 2, 1)
                temporal_pos_embed = torch.nn.functional.interpolate(
                    temporal_pos_embed, size=(new_t_size,), mode='linear', align_corners=False
                )
                temporal_pos_embed = temporal_pos_embed.permute(0, 2, 1)
                checkpoint_model['temporal_pos_embedding'] = temporal_pos_embed

        elif 'pos_embed' in checkpoint_model:
            pos_embed_checkpoint = checkpoint_model['pos_embed']
            embedding_size = pos_embed_checkpoint.shape[-1] # channel dim
            num_patches = model.patch_embed.num_patches # 
            num_extra_tokens = model.pos_embed.shape[-2] - num_patches # 0/1

            # we use 8 frames for pretraining
            orig_t_size = args.orig_t_size // model.patch_embed.tubelet_size
            new_t_size = args.num_frames // model.patch_embed.tubelet_size
            # height (== width) for the checkpoint position embedding
            orig_size = int(((pos_embed_checkpoint.shape[-2] - num_extra_tokens)//(orig_t_size)) ** 0.5)
            # height (== width) for the new position embedding
            new_size = int((num_patches // new_t_size) ** 0.5)
            
            if orig_t_size != new_t_size:
                print(f"Temporal interpolate from {orig_t_size} to {new_t_size}")
                tmp_pos_embed = pos_embed_checkpoint.view(1, orig_t_size, -1, embedding_size)
                tmp_pos_embed = tmp_pos_embed.permute(0, 2, 3, 1).reshape(-1, embedding_size, orig_t_size)
                tmp_pos_embed = torch.nn.functional.interpolate(tmp_pos_embed, size=new_t_size, mode='linear')
                tmp_pos_embed = tmp_pos_embed.view(1, -1, embedding_size, new_t_size)
                tmp_pos_embed = tmp_pos_embed.permute(0, 3, 1, 2).reshape(1, -1, embedding_size)
                checkpoint_model['pos_embed'] = tmp_pos_embed
                pos_embed_checkpoint = tmp_pos_embed

            # class_token and dist_token are kept unchanged
            if orig_size != new_size:
                print("Position interpolate from %dx%d to %dx%d" % (orig_size, orig_size, new_size, new_size))
                extra_tokens = pos_embed_checkpoint[:, :num_extra_tokens]
                # only the position tokens are interpolated
                pos_tokens = pos_embed_checkpoint[:, num_extra_tokens:]
                # B, L, C -> BT, H, W, C -> BT, C, H, W
                pos_tokens = pos_tokens.reshape(-1, new_t_size, orig_size, orig_size, embedding_size)
                pos_tokens = pos_tokens.reshape(-1, orig_size, orig_size, embedding_size).permute(0, 3, 1, 2)
                pos_tokens = torch.nn.functional.interpolate(
                    pos_tokens, size=(new_size, new_size), mode='bicubic', align_corners=False)
                # BT, C, H, W -> BT, H, W, C ->  B, T, H, W, C
                pos_tokens = pos_tokens.permute(0, 2, 3, 1).reshape(-1, new_t_size, new_size, new_size, embedding_size) 
                pos_tokens = pos_tokens.flatten(1, 3) # B, L, C
                new_pos_embed = torch.cat((extra_tokens, pos_tokens), dim=1)
                checkpoint_model['pos_embed'] = new_pos_embed

        utils.load_state_dict(model, checkpoint_model, prefix=args.model_prefix)

    model.to(device)

    model_ema = None
    if args.model_ema:
        model_ema = ModelEma(
            model,
            decay=args.model_ema_decay,
            device='cpu' if args.model_ema_force_cpu else '',
            resume='')
        print("Using EMA with decay = %.8f" % args.model_ema_decay)

    model_without_ddp = model
    n_parameters = sum(p.numel() for p in model.parameters() if p.requires_grad)

    print("Model = %s" % str(model_without_ddp))
    print('number of params:', n_parameters)

    total_batch_size = args.batch_size * args.update_freq * utils.get_world_size()
    num_training_steps_per_epoch = len(dataset_train) // total_batch_size
    args.lr = args.lr * total_batch_size * args.num_sample / 256
    args.min_lr = args.min_lr * total_batch_size * args.num_sample / 256
    args.warmup_lr = args.warmup_lr * total_batch_size * args.num_sample / 256
    print("LR = %.8f" % args.lr)
    print("Batch size = %d" % total_batch_size)
    print("Repeated sample = %d" % args.num_sample)
    print("Update frequent = %d" % args.update_freq)
    print("Number of training examples = %d" % len(dataset_train))
    print("Number of training training per epoch = %d" % num_training_steps_per_epoch)

    num_layers = model_without_ddp.get_num_layers()
    if args.layer_decay < 1.0:
        assigner = LayerDecayValueAssigner(list(args.layer_decay ** (num_layers + 1 - i) for i in range(num_layers + 2)))
    else:
        assigner = None

    if assigner is not None:
        print("Assigned values = %s" % str(assigner.values))

    skip_weight_decay_list = model.no_weight_decay()
    print("Skip weight decay list: ", skip_weight_decay_list)

    amp_autocast = contextlib.nullcontext()
    loss_scaler = "none"
    if args.enable_deepspeed:
        loss_scaler = None
        optimizer_params = get_parameter_groups(
            model, args.weight_decay, skip_weight_decay_list,
            assigner.get_layer_id if assigner is not None else None,
            assigner.get_scale if assigner is not None else None)
        model, optimizer, _, _ = ds_init(
            args=args, model=model, model_parameters=optimizer_params, dist_init_required=not args.distributed,
        )

        print("model.gradient_accumulation_steps() = %d" % model.gradient_accumulation_steps())
        assert model.gradient_accumulation_steps() == args.update_freq
    else:
        if args.distributed:
            model = torch.nn.parallel.DistributedDataParallel(model, device_ids=[args.gpu], find_unused_parameters=True)
            model_without_ddp = model.module

        optimizer = create_optimizer(
            args, model_without_ddp, skip_list=skip_weight_decay_list,
            get_num_layer=assigner.get_layer_id if assigner is not None else None, 
            get_layer_scale=assigner.get_scale if assigner is not None else None)

        if not args.no_amp:
            print(f"Use bf16: {args.bf16}")
            dtype = torch.bfloat16 if args.bf16 else torch.float16
            amp_autocast = torch.cuda.amp.autocast(dtype=dtype)
            loss_scaler = NativeScaler()

    print("Use step level LR scheduler!")
    lr_schedule_values = utils.cosine_scheduler(
        args.lr, args.min_lr, args.epochs, num_training_steps_per_epoch,
        warmup_epochs=args.warmup_epochs, start_warmup_value=args.warmup_lr, warmup_steps=args.warmup_steps,
    )
    if args.weight_decay_end is None:
        args.weight_decay_end = args.weight_decay
    wd_schedule_values = utils.cosine_scheduler(
        args.weight_decay, args.weight_decay_end, args.epochs, num_training_steps_per_epoch)
    print("Max WD = %.7f, Min WD = %.7f" % (max(wd_schedule_values), min(wd_schedule_values)))

    criterion = torch.nn.MSELoss()

    print("criterion = %s" % str(criterion))

    if args.eval:
        if args.resume:
            checkpoint = torch.load(args.resume, map_location='cpu')
            print("Load ckpt from %s" % args.resume)
            checkpoint_model = None
            for model_key in args.model_key.split('|'):
                if model_key in checkpoint:
                    checkpoint_model = checkpoint[model_key]
                    print("Load state_dict by model_key = %s" % model_key)
                    break
            utils.load_state_dict(model_without_ddp, checkpoint_model, prefix=args.model_prefix)
        else:
            utils.auto_load_model(
                args=args, model=model, model_without_ddp=model_without_ddp,
                optimizer=optimizer, loss_scaler=loss_scaler, model_ema=model_ema)

        preds_file = os.path.join(args.output_dir, str(global_rank) + '.txt')
        _ = final_test(
            data_loader_test, model, device, preds_file, amp_autocast,
            ds=args.enable_deepspeed, no_amp=args.no_amp, bf16=args.bf16,
        )
        torch.distributed.barrier()
        if global_rank == 0:
            print("Start merging results...")
            final_loss = merge(args.output_dir, num_tasks)
            print(f"MSE Loss of the network on the {len(dataset_test)} test videos: {final_loss:.2f}")
            log_stats = {'Final MSE Loss': final_loss}
            if args.output_dir and utils.is_main_process():
                with open(os.path.join(args.output_dir, "log.txt"), mode="a", encoding="utf-8") as f:
                    f.write(json.dumps(log_stats) + "\n")
        exit(0)

    utils.auto_load_model(
        args=args, model=model, model_without_ddp=model_without_ddp,
        optimizer=optimizer, loss_scaler=loss_scaler, model_ema=model_ema)
        
    print(f"Start training for {args.epochs} epochs")
    start_time = time.time()
    min_val_loss = 10000.0
    for epoch in range(args.start_epoch, args.epochs):
        if args.distributed:
            data_loader_train.sampler.set_epoch(epoch)
        if log_writer is not None:
            log_writer.set_step(epoch * num_training_steps_per_epoch * args.update_freq)
        train_stats = train_one_epoch(
            model, criterion, data_loader_train, optimizer,
            device, epoch, loss_scaler, amp_autocast, args.clip_grad, model_ema,
            log_writer=log_writer, start_steps=epoch * num_training_steps_per_epoch,
            lr_schedule_values=lr_schedule_values, wd_schedule_values=wd_schedule_values,
            num_training_steps_per_epoch=num_training_steps_per_epoch, update_freq=args.update_freq,
            no_amp=args.no_amp, bf16=args.bf16
        )
        if args.output_dir and args.save_ckpt:
            utils.save_model(
                args=args, model=model, model_without_ddp=model_without_ddp, optimizer=optimizer,
                loss_scaler=loss_scaler, epoch=epoch, model_name='latest', model_ema=model_ema)
        
        if data_loader_val is not None:
            test_stats = validation_one_epoch(
                data_loader_val, model, device, amp_autocast,
                ds=args.enable_deepspeed, no_amp=args.no_amp, bf16=args.bf16,
            )
            timestep = time.strftime("%Y-%m-%d %H:%M:%S", time.localtime())
            print(f"[{timestep}] Loss of the network on the {len(dataset_val)} val videos: {test_stats['loss']:.1f}")
            if min_val_loss > test_stats["loss"]:
                min_val_loss = test_stats["loss"]
                if args.output_dir and args.save_ckpt:
                    utils.save_model(
                        args=args, model=model, model_without_ddp=model_without_ddp, optimizer=optimizer,
                        loss_scaler=loss_scaler, epoch=epoch, model_name='best_val', model_ema=model_ema)

            print(f'Min Val Loss: {min_val_loss:.2f}')
            if log_writer is not None:
                log_writer.update(val_loss=test_stats['loss'], head="perf", step=epoch)

            log_stats = {**{f'train_{k}': v for k, v in train_stats.items()},
                         **{f'val_{k}': v for k, v in test_stats.items()},
                         'epoch': epoch,
                         'n_parameters': n_parameters}
        
        else:
            log_stats = {**{f'train_{k}': v for k, v in train_stats.items()},
                         'epoch': epoch,
                         'n_parameters': n_parameters}
            
        if args.output_dir and utils.is_main_process():
            if log_writer is not None:
                log_writer.flush()
            with open(os.path.join(args.output_dir, "log.txt"), mode="a", encoding="utf-8") as f:
                f.write(json.dumps(log_stats) + "\n")

    preds_file = os.path.join(args.output_dir, str(global_rank) + '.txt')
    if args.test_best:
        print("Auto testing the best model")
        args.eval = True
        utils.auto_load_model(
            args=args, model=model, model_without_ddp=model_without_ddp,
            optimizer=optimizer, loss_scaler=loss_scaler, model_ema=model_ema)
    _ = final_test(
        data_loader_test, model, device, preds_file, amp_autocast,
        ds=args.enable_deepspeed, no_amp=args.no_amp, bf16=args.bf16,
    )
    torch.distributed.barrier()
    if global_rank == 0:
        print("Start merging results...")
        final_loss = merge(args.output_dir, num_tasks)
        print(f"MSE Loss of the network on the {len(dataset_test)} test videos: {final_loss:.2f}")
        log_stats = {'Final MSE Loss': final_loss}
        if args.output_dir and utils.is_main_process():
            with open(os.path.join(args.output_dir, "log.txt"), mode="a", encoding="utf-8") as f:
                f.write(json.dumps(log_stats) + "\n")

    total_time = time.time() - start_time
    total_time_str = str(datetime.timedelta(seconds=int(total_time)))
    print('Training time {}'.format(total_time_str))


if __name__ == '__main__':
    opts, ds_init = get_args()
    if opts.output_dir:
        Path(opts.output_dir).mkdir(parents=True, exist_ok=True)
    main(opts, ds_init)
